Remark: According to normative regulations one shall set the temperature difference, if exact value is not known, accordingly. Buttons "5K (EN 6946)" and "10K (EN 10077) set this value to one of magnitudes required in these respective regulations.

For the very usual case of non rectangular air cavities normative regulations define following procedure to account for:

An equivalent conductivity is to be calculated for a fictive rectangular cavity. Such fictive cavity shall be constructed as follows:

create a rectangle surrounding the cavity of interest.

the area of a fictive cavity rectangle shall be equal to the area original (non rectangular) cavity.

the ratio of width to the height of the fictive rectangle cavity shall be the same as of the rectangle surrounding the original.

The conductivity calculated for such fictive rectangular cavity is the used instead for the (non rectangular) original air cavity.

Heat Stream direction: Definition of heat stream direction:

Horizontal (default)

Upwarads

Downwards

Thickness (stream dir.): The thickness of the cavity measured in the heat stream direction.

Remark: Thickness and width can be swapped via a context menu.

Width: The width of the cavity (perpendicular to the thickness)

Area: The actual are of the real (non rectangular) air cavity

Remark: Thickness and width can be swapped via a context menu.

Temperature difference dT: The difference of temperature between cavity boundaries in the heat stream direction.